Thursday, December 24, 2009

If you are curious, the resistance of a 300W type J halogen bulb, the ones you would find in those halogen torchiere lamps, is 3.3 ohms when cold. When it's hot it is 48 ohms, but that's a calculation only based on the wattage.

A warm halogen bulb in the near infrared

Since converting such a torchiere to CFL (but not in this project), I had an extra halogen bulb and debated throwing it out, but I figured they might make a decent power resistor. I used it in a project converting a PC ATX power supply to a benchtop 12V source. It works--but the hassle of cleaning the contacts for soldering, soldering, and placing such a large object in the case was enough to decide buying a power resistor in the first place is probably easier.

Wednesday, November 11, 2009

You can see the International Space Station in Chicago in the evening for the rest of the month. If schedules hold, you will also be able to see the Space Shuttle as it docks with the ISS, as the Shuttle should launch on the 16th.Here's the next 10 days.

Wednesday, October 28, 2009

One of the things I've always been interested in was radio; and part of that was scanning as much of the radio spectrum as possible to hear what was out there. As a kid, this was my father's shortwave receiver; I spent hours twirling the giant frequency handwheel on that radio absorbing every foreign radio broadcast I heard and wondering what the various weird noises I heard were.

For instance, at times there would be a overwhelmingly loud, rapid "thump-thump-thump" noise that was fairly broadband across a few megahertz. I asked my father about that and he called it the "Russian Woodpecker", an over-the-horizon radar system that used frequencies that were normally used by shortwave broadcasters. If I stayed up long enough at night, I would begin to pick up the European broadcasters waking up at dawn with their early morning news broadcasts.

One thing about most radios is you are only tuned to one frequency at a time. You get a limited amount of bandwidth around that frequency depending on how the radio works. It's hard hence to compare the strengths of two stations simultaneously without resorting to memory tricks or rapid tuning.

With a fancy piece of equipment called a spectrum analyzer, you can see a wide range of frequencies at once and see various radio stations, peaks, etc. To some extent you can do this with a PC sound card hooked up to the audio output of the radio, but again you are limited in bandwidth. See the laptop display below, for instance.

The generalized setup. An antenna, a diode detector, and an oscilloscope. The PC is not being used in this particular example.

What amazes me is a sub-$1000 digital oscilloscope that is advertised as a 40MHz scope, that is, it can display signals up to 40MHz in frequency, can in a FFT mode display the signals up to 500MHz and essentially function as a spectrum analyzer.

An overview of the Chicago radio spectrumThe key things to note here are intensity is the vertical, frequency is the horizontal. Near the upper right corner is "POS:", which notes the frequency at the center of the display. At the center bottom is the horizontal scale, in this case 25MHz per big division. So the bump of stuff to the left of center in this image is at about 125MHz-25MHz= 100MHz, which is in the FM Radio band.

FM Radio band.In the FM band, you can see that there are plenty of stations filling the available channels. The isolated peak on the left is WHPK-FM, the campus radio station running at 100W, and is about two blocks from my location. It sits in the non-commercial section of the FM band.

AM Radio bandThe AM radio band at my location is dominated by WRTO-AM at 1200kHz. This station gets into any cable, any wire, and if you have any rectification from a piece of corrosion, or just input an antenna directly into a PC, you will get La Tremenda.

Looking closer at 1200kHzIf you look closer at WRTO's signal, you see it has a strong carrier and two sidebands further out at about 12.5kHz out. Now, when I originally saved this image, I thought I was seeing the audio sidebands of the AM signal. If the AM radio station broadcasts a single note at 440Hz, for instance, you'd see the strong carrier, and two line peaks on either side at 440Hz away. But here they are all the way out at 12.5kHz, a frequency that is present in "ssss" or a cymbal but little else. And especially not normal AM radio broadcasting, which is limited by the FCC to just a tad over 20kHz bandwidth, so the stations have to drop all their treble sounds.

It appears these outliers are the dreaded "HD radio", a hybrid technique that transmits the audio in two sidebands that exceed the normal width of an AM broadcast. Unfortunately this process violates old technical standards that allowed stations to coexist with each other. It was dropped in favor of a proprietary digital standard that allows big stations to use more bandwidth and clog up the airwaves with digital hash noise.

Below the AM radio band

Just below the AM band is the rest of what is known as Mediumwave or Medium Frequency, which then transitions into LW or longwave; this band is notable for non-directional beacons for aeronavigation, DGPS (or differential GPS), and lots of noise. I will have to take another spin around this band to listen to some of those peaks and see if they are real signals.

VLF Radio spectrumOnce you get down here, you start running into lots and lots of switching mode power supply noise. Various Navies around the world still broadcast on this frequency for radionavigation and uninterruptible worldwide coverage. Two of the stronger signals to the left are probably the Russian radionavigation system at 11.9kHz and 12.6kHz.

I have some other snapshots showing excellent response to the shortwave radio broadcasters of the world. It's amazing to see the whole shortwave spectrum at once instead of moving around frequencies one kilohertz at a time.

Thursday, September 24, 2009

This circuit connected to my geiger counter uses on average 80uA-- that's 0.08mA. On a click, it will bump up to 0.1mA. On startup just for a second it uses 3mA. At those rates, and with a standard 9V battery (at 650mAh), it would run about 9 months continously.

Monday, July 27, 2009

If you are searching for ISS and Shuttle passes over Chicago, tonight's was the last one for a while. If you are an early morning person, mid August will work; if not, early September is the next time you can see the ISS in Chicago.

Tuesday, July 07, 2009

I just watched an awesome pass of the International Space Station over Chicago. I was able to catch it and follow* the ISS through a telescope at about 50x: the space station appeared as an eagle with orange solar panel wings, with a white body and a small white point source on the main axis. It was excellent, and that was at low power! Here was Tyrell's approach three years ago.

*follow in the sense of every twenty seconds moving a giant dome, followed by a german equatorial telescope in advance of the ISS and hoping I wasn't too slow.

Here are the highlights for the evening passes, when they begin, how bright they are, and how high in the sky; click on the link above to get the full details. In some cases you will be able to see the ISS on successive orbits.

Thursday, July 02, 2009

I've annotated a previous image of the moon with the location of the image: The orange markers are at the crater Hell E, which is listed in the press release as being just a few kilometers west of the image site. Hell E is listed as 10km across, so the images are just a touch to the right of that crater. Click on the image for a large original.

Monday, June 29, 2009

Seth Anderson at B12 Solipsism has an excellent series of posts (here, here, and here) about the intersection of the new online/sharing culture, copyright, and photography.

The first post is about the issue of copyright and fair use--many people fail to understand that "fair use" means you have already violated copyright, but you have a valid legal excuse. In photography, Seth points out that the ability to take an excerpt is potentially not possible, leaving every use of a photograph without permission a copyright violation.

The second post is a dust-up by a writer for the New York Times, who argued it was okay to print out a copy of any Flickr photograph and put it up in your private residence. This did not go over well with people who create--i.e., the photographers. While it may be ok for certain Creative Commons and Public Domain photographs, it is a violation of copyright to do that to a owned photograph. The legal question is, as I mentioned above, is this use considered Fair? You would be surprised at the muddled mess in the case law. A professor for instance lost a copyright case because he made personal copies of many science papers and kept them in his office. The turning distinction on that case was the amount of papers he made copies of that drove the copyright violation from "fair use" to a civil violation. Is one printed photo fair use? What if you decorate your whole apartment with them? What size can your print fairly? What about your friends' apartments?

The issues are completely muddy and complex--as a photographer, for instance, I feel I should be compensated for my work. Websites like say Chicagoist or Treehugger use flickr CC shared images to illustrate their stories. In the traditional media, the photographer would be compensated for their work, either by being employed or by a fee. This is not being done at all for most of the non-traditional sites on the internet. It is also a truth that these sites probably couldn't afford the going rate for photographs. Getting your image out for people to see for a photographer is a very important thing, but is it driving the image creation business out of a profession and into the hands of casual photographers? (The latin term amateur is perfect for here but misused--these photographers love what they do and are often just as good as a pro, but the amateurs are not paid).

You would be surprised what it costs to get the rights to every photograph in a magazine. Years ago I was paid once for an image covering less than 1/4 of a page in a small publication more than it costs for ten years of Flickr Pro. More recently, if someone can't get the image use for free, they move on to find another CC licensed image. At what point do I give away my images? For specific charity non-profits? For non-profits? The National Geographic Society is a non-profit, should they get images for free? For school textbooks? For medical school textbooks? There are no good answers, except I am sure there will be fewer pro photographers out there in the future.

There is also the new culture driven out of the Free Software/File Sharing culture where the belief is all content is free and the driving force behind creation of works is not the desire to make money; if you make money you have to find a way to do it selling something tangible, whether it be technical support, concerts, or physical items. This belief is moving beyond the software paradigm, is being fought in the music and movie industries (and being lost completely by the industries), and now is moving into books, photography, and other creative markets. Google was asking illustrators to create for free custom themes for the search engine. Google, a company with a 134 Billion market capitalization, was asking artists to work for free.

I benefit from many of these changes. I listen to music online (and I also still buy CDs, old fashioned me). I work in a field that utilizes free software every day. It is conflicting internally to know that somewhere an artisan may end their craft because they cannot afford to continue, because I chose the free option. I also know there are things I cannot do unless the cost is cheap enough for me to afford. For me, much work remains to allow the creative domains and artists the ability to ply their crafts in the future. I do not know how to get there from here.

Friday, June 12, 2009

I watched the end of analog TV at noon today for Channels 2,5, and 7. They unceremoniously just cut the power--one in a commercial and two in soaps. Fox 32 is still broadcasting in analog with a constant scroll, and all the low-power and non-profits are still on, save WTTW.

Monday, June 08, 2009

I used to record audio off my Tivo on my desktop computer--but when I had the cable TV connected, I would get a loud hum. The reason for this is related to the idea of "ground" in electrical systems, which are used as a reference point for zero voltage and/or safety purposes. The kicker was the cable TV cable offered a different path to ground compared to the PC's ground.

For consumer generic audio connections, the audio signal (a varying AC voltage of about one volt) is compared to the ground of the system. Hence the two connectors on an RCA connector, signal and ground, or three connectors on a stereo jack: left, right, and ground. If your ground happens to be varying up and down at 60 times a second (because it's not a good ground, for instance), you will also get that hum on your output.

For some professional audio systems, the reference ground is brought with the signal, so you have three connections for any channel. When both the signal and ground vary up and down in sync, it's easy to subtract the pickup noise and have a clean signal.

In simple, single systems, either approach works fine. The problem is when you start interconnecting equipment.

I made a stereo isolation audio transformer to solve this problem. The left and right channels enter a 1:1 600ohm audio transformer, which transmits the audio signal (which is AC) but blocks any DC connection. This prevents ground loops and currents between the two devices. I got the two transformers from old modems. One of the jacks is a fancy panel mount, the other is from an old sound card, and this old one is actually needed, because it is plastic, isolating it from the case, which is connected to the ground of the panel mount jack. Of course, I put everything in an Altoids tin.

I suppose it would also help if I put some ferrite on the inputs to also reduce RFI/EMI problems, but I haven't yet. Just having this device between a shortwave radio and a PC has reduced interference pickup quite a bit.

You can see more photos of the build at http://www.flickr.com/photos/dwarmstr/sets/72157604679420753/. Essentially, 1. Measure and Mark your holes. 2. Make a small punch to keep drill centered. 3. Drill a pilot hole, then the right size. 4. Solder the connections. I used a multimeter to figure out which connection was which on the transformers. 5. Hot glue for stability.

Monday, May 18, 2009

The European Space Agency launched an ambitious set of satellites a few days ago: Herschel is a 3.5m diameter infrared telescope, and Planck is a cosmic microwave background telescope. Both are planned to be placed in one of Earth's Lagrangian points called L2. Upon launch such large objects can be tracked with optical telescope for a while. Upon examining these images, astronomers found not two objects, but at first four, which turned out to be the booster rocket and the structure holding both satellite while launching (see here). But later, they found two more fainter objects. These objects have seemingly moved off of the Herschel/Planck trajectory. What were they? The other more disturbing news came today, when Jean-Claude Pelle of Southern Stars Observatories reported finding dozens of new objects in the same path. This implies a possible failure of one or more of the telescopes and would be a blow to science.

Tuesday, May 12, 2009

There are another set of convenient evening passes of the International Space Station over Chicago until the end of the month. Last night we watched it streak across the sky in five minutes from Ryerson. Through the telescope at low power it was two blazing white ovoids with two small orange dots on one of the white blobs.

Tuesday, April 21, 2009

I've heard this strong station several times now over the past year, usually later at night. It always broadcasts at 5900 kHz (or now that I think about it, have I picked it up at 9800kHz?). I picked this up Monday night/Tuesday morning, April 21st, just after 00:34 CDT (5:34 UT).

The station is pretty strong here in Chicago, with only occasional fading, and it sends a modified CW signal that can be picked up with any shortwave receiver. It only uses three digit code letters in groups of five: those Morse Code letters that are described by three combinations of dots and dashes, minus S and O, which are dot-dot-dot and dash-dash-dash.

Thursday, April 09, 2009

This such an auspicious year. I watched an interview on Chicago Tonight with one of the creators of "400 Years of the Telescope", to be broadcast on PBS this Friday. Immediately a shot of the Yerkes 40-inch refractor passed by in glorious HD, a scope I am intimately familiar with, and now I am compelled to watch. Friday at 8PM on WTTW. Of course, I am very happy when E.E. Barnard pops up on the schedule page on the site--Barnard's experimentation with astrophotography has a tie to the RAS observatory: our 1895 Warner and Swasey mount was first lent to Yerkes Observatory so Barnard could test camera lenses.

Tuesday, April 07, 2009

Joe Cottral managed to get a spare 2.5m satellite dish from western Illinois to Chicago. The rest of the RAS had the responsibility of getting the dish from ground level up to our 6th floor aerie. We decided on raising the dish as reasonably quickly as possible, to reduce the annoyance factor for all non-involved. We also picked after much observation and discussion to raise the dish via the southeast corner of Ryerson which is an elevated turret. The reason being the turret allowed easy transfer over the parapets of Ryerson. The loading dock offered easy vertical lift, and the fire escape offered quick one-story lifts, but in the end, Lui's suggestion of the turret was the superior option.

Now, we have to 1. acquire a receiver capable of 1420MHz and 1.6GHz-ish, 2. Clean up the dish mounting steel, 3. Mount the dish on Ryerson with lots of Quikcrete, 4. Get microwave-capable cable, 5. get a low-noise-amplifier, and 6. put it all together. Minor bit there. Oh yes, and decide where to place it on the roof.

Friday, March 27, 2009

This is from a Japanese weather satellite staring at the Western Pacific, and the volcano is near the limb of the Earth from its perspective.Picture Date: March 26, 2009 17:30:00Image Creator: Dehn, Jonathan / NWS

Tuesday, March 24, 2009

When John Crocker and I built the RAS solar spectroscope (see some of the spectra here), we had no budget for the project. We used what was available and free for us to use; so we used blue acrylic as the structural material of the spectroscope; razor blades for the slit; spare singlet convex lens for the collimator, a surplus finderscope as the viewing scope; and finally, we bought 3 "defective" surplus reflection gratings from Edmund Scientific. This was the special--they were defective in some manner, enough to fail some sort of specification, but not enough to be truly defective. You couldn't specify resolution or anything; so we bought three on the correct thought that one of them would likely match our specs.

Over the years the aluminum corroded and was giving a lot of scatter in the spectroscope; what this did was create a gray mush on top of the spectrum. So I endeavored to get the grating recoated.

Fluorescent light spectrum

Eventually, I discovered someone willing to use a coating machine on campus to recoat the grating. This meant I should prepare the grating for recoating, and I removed it from the spectroscope for a bath. Standard techniques for removing aluminum off of glass require something that will dissolve the metal but not hurt the glass surface. NaOH is out as it like many bases will etch glass. Instead a good acid is needed. Nitric is popular, but I did not have any. I thought about glacial acetic acid, since we have some as stop bath. But I realized I had hydrochloric acid, another excellent acid for this process. That source was toilet bowl cleaner. I had some already, instead of going to the hardware store for muriatic acid (an obsolete name for hydrochloric). A note: depending on your retailers, the muriatic acid at the hardware or pool store may be cheaper than toilet bowl cleaner. It is certainly a purer source.

A view of the oxidized old coating.

Smells fantastic, but don't breathe deeply. Acid fumes.

After a while I was concerned the metal was not coming off. A test piece of aluminum foil started dissolving in minutes, so I knew the problem was with the grating. Some old coatings can have such a thick aluminum oxide coating that the underlying metal is protected from the acid, and one trick is to damage the coating via a pinprick or scratch near the edge. I decided to try scotch tape--it can remove surfaces nicely.

A first pass pulled off half the aluminum coating, oxide and all. Success! I could see the grating underneath. But disaster struck on the second pass.

You see, I had assumed the grating was actually on the glass: a long repetition of grooved lines in the glass. Instead, it was a thin layer of plastic replica glued on top. The second pass with tape removed the grating, leaving me with a worthless piece of frosted glass. So much for a simple near-zero cost for repairing the spectroscope. But now I have wintergreen-smelling fresh glass squares.

Wednesday, March 18, 2009

Leo 1 is a dwarf galaxy located about 800,000 light years away in the constellation Leo. In fact, you can nearly pinpoint the location of the galaxy with your naked eye by looking at the bright blueish star Regulus. (You can find Regulus, if you don't know many constellations, by looking at the Big Dipper. Know the pointer stars on the bowl that point to Polaris? If you go backwards from them, they point to Regulus). Regulus is only a 1/3 a degree away from this galaxy, and its glare is always in the way. Take a look at this fantastic image from Russell Croman

Occasionally slightly crazy, I decided to attempt to image this galaxy last Friday. The moon had just risen and it was slightly hazy. In other words, I was completely crazy.

About 45 minutes exposure. Click to enlarge

It's tough to see, but look at the slightly knobbier noise just to the bottom right of center. Compared that to the noise in the rest of the image. You can use the two stars in the upper left to compare the frame with this image from Wikipedia/Digital Sky Survey/STScI:

Sunday, March 15, 2009

We get some reasonably good passes of the International Space Station and the Shuttle here in Chicago the next few evenings. Take a look. The Shuttle will dock in three days at the ISS, so until then watch for the Shuttle trailing the ISS in the orbit. You might even see them quite close together in the sky during the pass.

Thursday, March 12, 2009

Were you wondering about the Republican response to the State of the Union speech where Gov. Jindal derided the '$140 million for something called "volcano monitoring."'? Me too. I did a double-take, and I assume most others with geoscience backgrounds did too. Regardless of your political leanings, I would assume people would want to know if a volcano erupted (say while you were in a jet plane heading to Japan) or what the risk was if there were an eruption (if you lived in a possible lahar zone, like parts of Tacoma, for instance).

Monday, March 09, 2009

Click to enlarge. A total of 53 images, each 15 seconds each, totaling 13:25 minutes. Taken on December 29th, 2008.

42 Orionis is a bright B1 star in Orion's sword, just to the north of the spectacular Orion Nebula (M42 & M43). It is always overshadowed by its neighbor and many miss the NGC 1977 nebula entirely because the Orion Nebula is almost always glowing in the field of view and very distracting. NGC 1973 is the nebula surrounding the star in the upper right of the frame. 42 Orionis itself is the bright star just to the right of center. The bright star to the left of center is 45 Orionis, an unrelated foreground (370 ly away) star. Unwritten is that this nebula is part of the same giant Orion Molecular Cloud complex that the Orion Nebula is part of.

As always, I am never happy with processing. On this one, there were a significant number of sub-images that were trailed. Normally I align all the subframes and then add the subs together. Since adding will send the pixel values all to 32767 (I use Iris, which is limited to 16 bits), in most cases I utilize either a median combine (which will get rid of the trails) or use "add_norm", which normalizes the final result to fit in 16 bit space. However in this one, I first multiplied all the values in all the images by 0.02, then added them all up, then I subtracted the images I knew were trailed. Some modified equalization and a touch of gamma, and all done. Until I am unsatisfied again.

Thursday, March 05, 2009

I created this project originally for the Sights and Sounds of Science contest which was sponsored by the Chicago Materials Research Center of the University of Chicago. This particular version was made for the Five-Minute Film Festival sponsored by NSIT.

Nanocrystals are small collections of several hundred to hundred thousand atoms arranged in a crystal matrix. Quantum dots are nanocrystals made of semiconductors, and the several hundred atoms act like one giant molecule with regards to their electrons with variations in energy levels due to the size of the dot. The smaller the dot, the higher photon energy released during fluorescence.

This video was compiled from fluorescing colloidal quantum dots of different sizes excited by an argon laser. The dots are invisible (with one exception in a microscope at 2:14) but they produce the bright colors in the beam. The bits of bright blue flashes are dust particles in the solutions.

The music is from Ms. John Soda, the song is "Technicolor" from the album No P. or D.

Tuesday, February 24, 2009

The RAS observed Comet Lulin in Chicago yesterday. Unforunately it wasn't 100% clear, with some sort of high cirrus haze up, and with all the light pollution, only two of us saw the blob that was the comet. For proof of where it was, I took a quick snapshot through the eyepiece to confirm the location for others looking.

We present an overview and a status report of HYPERMUCHFUSS (HYPER velocityor Massive Unseen Companions of Hot Faint Underluminious Stars Survey) aimingat the detection of a population of high velocity subluminous B stars and whitedwarfs. The first class of targets consists of hot subdwarf binaries withmassive compact companions, which are expected to show huge radial velocityvariations. The second class is formed by the recently discoveredhyper-velocity stars, which are moving so fast that the dynamical ejection by asupermassive black hole seems to be the only explanation for their origin.Until now only one old hyper-velocity star has been found, but we expect alarger population. We applied an efficient selection technique for hotsubdwarfs and white dwarfs with high galactic restframe velocities from theSDSS spectral data base, which serve as first epoch observations for ourcampaign with the ESO VLT and NTT in Chile, the 3.5 m telescope at DSAZobservatory (Calar Alto) in Spain and the WHT on La Palma. The survey isnearing completion and provides us with promising candidates which will befollowed up to measure their RV-curves to uncover massive companions or provetheir nature as HVS.\\ ( http://arxiv.org/abs/0901.1030 , 1617kb)

Wednesday, February 11, 2009

Two satellites collided in orbit two days ago, creating a spray of debris that will have to be closely watched to avoid further collisions. One satellite was an Iridium, one of the 88 or so in orbit (I see it was #33), and the other was a non-functioning Russian Cosmos satellite. I hope the Cosmos had either ejected the nuclear reactor that some of them use or was non-nuclear. I see another nuclear Cosmos had a problem recently. What's interesting about this collision was the height: at 490 miles, the debris is fairly high enough to have some significant lifetime. As debris densities increase, chances of collision greatly increase, greatly increasing debris densities, increasing collisions, which... you get the idea. These sort of things are really bad for our near Earth environment.

Saturday, February 07, 2009

This was taken on Thursday. Click to enlarge. 2427x2599. A composite of 6 sets of images. Each set is approximately 30 subexposures of 1/1000 seconds. Processed with Registax, Autostitch, and Photoshop.

Friday, February 06, 2009

Sometimes I feel for the fellows working the Science press racket. They have to distill the complicated nature of research science into a tidbit that the mainstream media will be able to digest and regurgitate into yet another tidbit.

But sometimes I am annoyed. I feel the words "strange", "mysterious", "hidden", and "stunning" have no place in a science press release. The best ones use direct references to the science, do not declare commonly known principles or phenomena as "mysterious", and work their best to educate the reader about the science being done. They do not use poor analogies. I know a few of the writers, and sometimes problems like these develop not from them but from their employers.

This is not that. And the Register called him out on it. It is in no way the worst example of the science press release. I would be more sympathetic if the writer would take the Register's criticism to heart about that analogy.

Thursday, February 05, 2009

A moon mosaic from last night. I didn't take the images or process them; Will did all that. The only thing I've done is run it through Autolevel in Photoshop. For processing, we took about thirty images each of each section of the Moon with the SXV-H9 camera at 1/1000s, and then ran each set through Registax to get the sharpest ones, then used Autostitch to put the sets together.

Sunday, January 25, 2009

I made a few videos of the simple microwave / 2.4GHz meter dealing with work office's microwave oven--woe be unto whomever hangs around the hinge.

The first is a full examination of the space of the microwave oven, and is entirely inappropriate for those with short attention spans (stick to the second video, you).

This one is a short proof the detection is when the microwave oven is busily heating my hot water for tea.

The other amazing news is there is a very strong microwave signal that the northwest corner of the roof of Ryerson intercepts that appears to be coming from either the Admin building or the hospital: it strongly peaks in the southwest direction, almost pegs the meter on the 200mV scale, and when I added a headphone to the meter I could audibly hear some sort of signal that reminded me of a TV video sync noise.What is this signal? Am I hearing a horizontal sync? Or is there some other signal that has a repetitive sync noise that runs at 12-18 kilohertz?

Thursday, January 22, 2009

Here's a band scan of all FM radio stations heard Wednesday night in Chicago with a Degen 1103. I attached it to two random length wire dipoles, oriented north/south and east/west and could switch between the two.

For medium and low strength stations, I used the FCC database for various queries:for all stations within 100km of me, for instance, click here.

You can get radio coverage maps from the FCC, or more refined maps from Radio Locator that show how likely it is to pick up the station.

Antenna is the orientation of the dipole; so the note "east/west" means the wire is strung east/west and sensitive to signals coming from the north or south.Station IDs were either heard, inferred from strength, music type, from the list of Chicago stations, or best guess from distant station lists.

If a frequency is not listed, it was a channel subject to bad interference from a neighboring station.

The idea of finding the clear channels is to find one suitable for meteor scatter work: a normally too-distant station (because it is over the horizon) can suddenly boom in because the signal is reflected from a ionized meteor trail halfway between the listener and broadcaster.

Some interesting results: WXXC and WBYR, located in Marion and Fort Wayne, IN, at 150 miles away.